Method of treating veneer



Patented I Sept. 6, 1932 PATENT OFFICE EMIL LOETSCHER, OF DUBUQUE, IOWA METHOD OF TREATING- VENEER No Drawing.

The object of this invention is to overcome the great difliculty encountered with thin natural wood veneer when used with phenol condensation products, caused by natural resins in the veneer uniting with the phenol condensation products producing a sticky substance which causes the product to adhere so firmly to the press platen that it cannot,

in many cases be removed therefrom, without tearing the wood veneer and the product to ieces.

While this does not happen with all woods, it is particularly common in the cases of walnut and of oak. It depends somewhat upon the nature of the wood and the amount of resin in the wood. I

It is obvious that in veneering panels or other articles by a process which employs phenol condensation products as a cementing material as well as afinish, that even a slight spot-sticking of the veneer would spoil the product, since no way has been discovered by which the spot can be finished to the same high degree and. polish of the finish of the material surrounding the spot. In many cases the adhesion is so strong that the veneer, together with part of the base or core.

material is torn to pieces. Even if only a small percentage of the work causes trouble 0 from this source, it would make an impractical operation in usingphenol condensation products because the work which is spotted is a total loss.

The present invention, in addition to preventing sticking of veneer to the press platen,

has the further advantage of materially removing the color of the veneer and of replacing the same by stains which give the exact and uniform shade of color desired. Some 40 natural woods change in color, due to the heat of the process of applying phenol condensation products, and by removing the color with a bleaching agent, the correct color can be restored with a suitable stain or stains or aniline dyes,

In practicing the method of this invention in connection with thin wood veneers, (in most cases 1/100 in thickness,) the veneer sheets are arranged vertically in racks and immersed in an agitated or circulated solu- Application filed. August 22, 1931. Serial No. 558,836.

tion capable of removing the natural resins from and of bleaching the veneer. A 5% solution of sodium hydroxide is satisfactory. for the purposes though harsh on the veneer, and a more satisfactory solution consists of 2 70 solution of sodium carbonate with El sodium bicarbonate. Sodium perborate also fills the requirements. Other agents, such as ordinary bleaching powder, calcium hydroxide, ammonium carbonate, and po- 60 tassium permanganate have each been found effective, and applicant does not care to be restricted to any particular chemical, but desires to cover any agent for producing the stated result.

After the Veneer-sheets have been soaked or treated in any of these solutions, they are removed to another tank and thorou hly washed with water to remove all traces of the chemicals. The veneers are then allowed to drain.

The treated veneers may now be applied in their bleached state to the base or core material, but if they are to be colored, they are immersed, preferably edgeways in vertical position, into a vat containing a solution of ordinary wood stains, preferably of the pernianent stain type, or suitable aniline dyes. After dyeing, the veneers are removed from the color solution and dried, preferably be so tween sheets of absorbent basswood heated to a temperature of 150 F. or 200 F. and arranged flatways to avoid wrinkling or curling.

The veneer sheets are now coated, by immersion or otherwise, on both sides with phenol formaldehyde condensation product, such as bakelite, after which they are heated at a'moderate temperature of about 130 C. for six to ten minutes to remove most of the solvent therefrom. The veneers are then ready to be applied to the base or core material and subjected to pressure, between platens of a hydraulic press, in the presence of 95 heat sufficient to react the condensation prodnot. The condensation product on one side of the veneer cements it to the base or core material, while the condensation product on the side of the veneer next to the press platen 1 produces a varnish like finish coating on the exposed side of its veneer.

The heat and pressure employed to react the phenol condensation product would soften and cause natural resins to be forced from the cells of the wood veneer and by materially removing these natural resins, as above outlined, they are not present to break through or to unite with the finish coating to form the sticky substance that causes the veneer to stick to the press platen and cause surface spots that spoil the product.

Further, there will be no discolorations of the veneer, due to the temperature of the press platens causing some of the natural resins to react with the condensation product to cause dark discolorations, which are quite objectionable.

When the veneers are treated in this manner, the color thereof is very uniform and very much more beautiful than when the natural untreated veneers are used, even though the latter could be removed from the press platens without sticking.

Apart from its more important utility in connection with wood veneers, the invention has considerable value in connection with any cellulosic product having a surface coating of phenol condensation product wherein there is danger of the natural resins of the cellulosic material uniting with the phenol condensation product to cause spot sticking as in the case of veneered products.

While the term platen hasbeen adopted herein, it is not intended that its meaning should be restricted to a flat plate-like body, but that it should be accepted in its broader sense as meaning any surface whether plain or ornamental with which the product is pressed while the condensation product is being reacted to give it shape and from which the finished product must be readily released.

What I claim is 1. The method of coating an article containing cellulosic material with condensation product, consisting in removing natural resin from the cellulosic material then treating the cellulosic material with condensation product in a'manner to produce a film of the latter on the surface of the finished article, and subjecting the treated cellulosic mate- "ial to platen pressure and heat to react the condensation product.

2. The method of forming an article hav ing a condensation-product-coated covering of cellulosic material, consisting in removing natural resin from the cellulosic material, then treating the cellulosic material with condensation product in a manner to produce a film of the latter on the exposed surface of the finished article, applying the treated cellulosic material to a base with condensation product interposed, and subjecting the celin the presence of heat suflicient to react the condensation product.

3. The method of forming an article having a condensation-product-coated wood veneering, consisting in removing natural resin from wood veneer, then treating the wood veneer with condensation product in a manner to produce a film of the latter on the exposed surface of the finished article, applying the treatcd wood veneer to a base with an adhesive and subjecting the veneer and base to platen pressure in the presence of heat sufficient to react the condensation product.

4. The method of coating wood with condensation product, consisting in treating the wood with a bleaching agent having the property of removing natural resin from the wood, then treating the wood with condensation product in a manner to produce a film of the latter on the surface of the finished product, and then subjecting the wood to platen pressure in the presence of heat sufiicicnt to react the condensation product.

5. The method of coating wood with condensation product, consisting in treating the wood with a bleaching agent having the prop erty of removing natural resin from the Wood, coloring the wood, then treating the wood with condensation product in a manner to produce a film of the latter on the surface of the finished product, and then subjecting the wood to platen pressure in the presence of heat suflicient to react the condensation product.

In testimony whereof I aflix my signature.

EMIL C. LOETSCHER. 

